1. Field
The following description relates generally to wireless communications, and more particularly to handling radio link failure.
2. Background
Wireless communication systems are widely deployed to provide various types of communication content such as, for example, voice, data, and so on. Typical wireless communication systems may be multiple-access systems capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, . . . ). Examples of such multiple-access systems may include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and the like. Additionally, the systems can conform to specifications such as third generation partnership project (3GPP), 3GPP long term evolution (LTE), ultra mobile broadband (UMB), and/or multi-carrier wireless specifications such as evolution data optimized (EV-DO), one or more revisions thereof, etc.
Generally, wireless multiple-access communication systems may simultaneously support communication for multiple mobile devices. Each mobile device may communicate with one or more access points (e.g., base stations) via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from access points to mobile devices, and the reverse link (or uplink) refers to the communication link from mobile devices to access points. Further, communications between mobile devices and access points may be established via single-input single-output (SISO) systems, multiple-input single-output (MISO) systems, multiple-input multiple-output (MIMO) systems, and so forth. In addition, mobile devices can communicate with other mobile devices (and/or access points with other access points) in peer-to-peer wireless network configurations.
When communicating with one or more access points in a connected mode, however, a mobile device can experience radio link failure (RLF), which can occur when the mobile device loses connection to the one or more access points for a period of time. This can be caused by a deep fade of a signal from the one or more access points (e.g., where the mobile device is moving through a tunnel, across an area of varying altitude, in an elevator, and/or the like). The mobile device can detect the loss of signal (e.g., based on a degraded signal quality, receiving or not receiving cyclic redundancy headers, etc.) and can start a timer at the physical layer to determine RLF. Once this timer expires, the mobile device determines RLF has occurred and relies on upper layers to reinitialize connection with the one or more access points or disparate access points. In addition, for example, another timer can be specified during which connection is to be reinitialized by the upper layer before the mobile device switches to an idle mode. In 3GPP LTE, this can be a T311 or similar timer. In Wideband-CDMA, this can include T314 and/or T315 timers.